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April 26, 2009 -- Muscle cells taken from patients' own thighs can help reduce their treatment-resistant stress urinary incontinence.

It isn't a joke when, due to stress urinary incontinence, laughing or coughing makes your bladder uncontrollably leak urine. Most patients get help from exercises, behavioral training, and drug treatment; but many still leak too often.

Help may be on the way from a new therapy: taking muscle cells from the upper thigh and injecting them into the sphincter muscle that controls urine flow. The idea is to stimulate growth of new sphincter muscle cells via growth signals sent by the injected cells.

It just might work, suggest clinical trials sponsored by Cook MyoSite, the Cook Medical subsidiary that is developing the treatment. University of Toronto researcher Lesley K. Carr, MD, and colleagues treated 29 women with one or two injections of thigh muscle cells at various doses.

All of the women had stress urinary incontinence that had not improved over a year of standard therapy.

"Overall, urinary leaks were reduced after both injections," Carr reported at this week's annual meeting of the American Urological Association.

Of the 17 patients evaluated 12 months after the muscle-cell injections, 13 -- over three-fourths of the women -- had fewer stress leaks and less urinary urgency.

However, one woman had worse incontinence than she had before treatment. While none of the adverse effects of treatment was rated "serious," there was pain and bruising in the thigh, pain at the site of injection, and "mild and self-limiting urinary retention and urinary tract infection."

Despite these issues, 86% of patients chose to have a second muscle cell injection three months after the first.

American Urological Association spokesman Anthony Atala, MD, chairman of the Wake Forest University urology department and a leader in the field of tissue regeneration, said the study confirmed the muscle-cell treatment to be safe and effective.

"It is important to note that this therapy has few side effects and seems to improve symptoms for most patients in whom other therapies failed," Atala says in a news release.